Noise-protection embankments, walls or facades have been employed for some years in connection with the protection of citizens from traffic noise. On account of the large space requirement of embankments, these are preferably raised in open terrain; on the other hand, in the municipal domain, in the case of bridge structures and frequently also in the case of railway lines, noise-protection walls or facades find application.
In order not to exclude the car-driver or the passenger of a rail vehicle entirely from the environment despite the high walls--that is, as a precaution against a possible "tunnel effect" on bridges, for example--these walls are nowadays constructed so as to be partially transparent.
Stemming from the conventional technology for installing silicate glasses, transparent panes are set in frames, and in certain cases wire gratings are additionally intended to provide a safeguard by preventing fragments from falling down.
A generic noise-protection wall-segment, is known from DE 42 30 786 A1, for example. The segment that is presented therein consists of two perpendicular posts at the edges and a substantially rectangular frame which is fixed to the perpendicular posts at the edges and of a substantially rectangular sound-absorbing sheet. The frame exhibits two vertical frame crossbeams and an anterior stiffening crossbeam connecting the two upper end regions of the two vertical frame crossbeams and in contact with the latter, which likewise connects the two upper end regions of the two vertical frame crossbeams, being in contact with the latter, and which is attached in such a way as to be capable of being dismantled. The substantially rectangular sound-absorbing sheet is dimensioned so as to be capable of being inserted into the frame and is detachably retained in the latter.
From the dimensional design it is to be noted that the sound-absorbing sheet made of plastic which is inserted into the frame may be up to 50% higher than the frame or than the vertical frame crossbeams, so that for a given segment-height the frame has to have a height amounting to approximately 2/3 of the height of the sound-absorbing sheet.
Although the noise-protection wall-segments according to DE 42 30 786 enable the advantageous use of transparent plastic sheets, as a result of the essential use of the frame construction at approximately 2/3 of the height of the sound-absorbing sheets a visually "quite massive" impression is still conveyed. This is because the "free-standing portion", that is to say the part of the plastic sheets projecting beyond the frame construction, is important for the visual impression.
Moreover, in this way a relatively large proportion of the area of the relatively expensive plastic sheet is employed without achieving the desired effect, i.e. a large fraction of the plastic sheet is totally contained within the frame of the load-bearing structure, so that the intended slimmer effect is achieved only imperfectly or not at all.